Varying velocity sheet handler

ABSTRACT

A document creating apparatus comprising an image transfer system and a transport system for transporting sheets of material. The transport system has a first and second drive for moving the sheets of material. A controller is connected to the first drive and adapted to vary velocity of the first drive. While a sheet of material contacts the first drive, the controller decreases the velocity before the sheet of material contacts the second drive, and increases the velocity after the sheet of material contacts the second drive.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a sheet moving system and, more particularly, to a sheet moving system having a variable velocity.

[0003] 2. Prior Art

[0004] Many different sheet registration devices are known in the sheet feeding art. For example, U.S. Pat. No. 5,543,909 discloses a stalled roll registration apparatus and method used as the sole timing adjustment in a paper path which includes a clutch or motor driven registration nip, a buckle chamber and two sensors. As machine speed moves up, electronic registration methods are used but can be costly in comparison to a stalled roll registration apparatus and method. Electronic registration methods are used because with the increase in machine speed, the velocity at which the sheet impacts a registration nip in a stalled roll registration apparatus is sufficient to damage the sheet or sufficient to push the lead edge through the nip thereby degrading lead edge registration performance. There is a desire to provide a sheet moving system which provides an increase in machine speed but with the use of a low cost stalled roll registration apparatus.

SUMMARY OF THE INVENTION

[0005] In accordance with one embodiment of the present invention, a stalled roll registration system is provided for use in a document creating apparatus. A first drive is provided that has an idler roll and a drive roll for driving sheets of material at a variable velocity. A second drive is positioned downstream of the first drive that has an idler roll and a drive roll that is adapted for intermittent driving. A controller is connected to the first drive and adapted to vary the velocity. While the sheet of material contacts the first drive, the drive velocity is decreased before the sheet of material contacts the second drive, and the drive velocity is increased after the sheet of material contacts the second drive.

[0006] In accordance with another embodiment of the present invention, a document creating apparatus is provided comprising an image transfer system and a transport system for transporting sheets of material. The transport system has a first and second drive for moving the sheets of material. A controller is connected to the first drive and adapted to vary velocity of the first drive. While a sheet of material contacts the first drive, the controller decreases the velocity before the sheet of material contacts the second drive, and increases the velocity after the sheet of material contacts the second drive.

[0007] In accordance with another embodiment of the present invention, a method of moving a sheet of material in a document creating apparatus is provided comprising a first step of driving a first drive at a velocity to move the sheet. When a leading edge of the sheet approaches a second drive, the first drive velocity is decreased. After the sheet of material contacts the second drive, the first drive velocity is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein:

[0009]FIG. 1 is a schematic view of a document creating apparatus;

[0010]FIG. 2 is a schematic elevation view of a xerographic processing or printing section;

[0011]FIG. 3 is a schematic side view of a registration system;

[0012]FIG. 4 is a schematic side view of a registration system with a sheet of material approaching a second drive;

[0013]FIG. 5 is a schematic side view of a registration system with sheet of material in contact with a second drive;

[0014]FIG. 6 is a time chart of the velocity of the first and second drive rolls;

[0015]FIG. 7 is a time chart of the velocity of the lead edge of a sheet of material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] Referring to FIG. 1, there is shown, in schematic form, a view of a document creating apparatus 2 for creating documents in accordance with teachings of the present invention. Although the present invention will be described with reference to the single embodiment shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms of embodiments. In addition, any suitable size, shape or type of elements or materials could be used. A copying or printing system of the type shown is preferably adapted to provide duplex or simplex stacked document sets from duplex or simplex collated document or print sets which result from either duplex or simplex original documents or output document computer files for print.

[0017] Document creating apparatus 2, in the embodiment shown, is a copier. However, in an alternate embodiment, the apparatus could be a printer or any other suitable type of document creating apparatus. Document creating apparatus 2 generally comprises a xerographic processing or printing section 3, a finishing section 6 and an output section 9. Printing section 3 can be an electrostatographic printing system such as made by Xerox Corporation or alternately other xerographic or other type of printing apparatus. Printing section 3 incorporates an image transfer system and a transport system for transporting sheets of material. Finishing section 6 may typically incorporate a hole punch, a stapler, or any other suitable type of feature known in the art. Output section 9 incorporates a tray 11 or a bin sorter that accepts and stacks documents or document sets output from finishing section 6 at output zone 12. Documents are printed or copied in printing section 3 and output from printing section 3 to finishing section 6. Documents can be sorted and bound at finishing section 6. Document sets can be output from finishing section 6 at output zone 12.

[0018] Referring now also to FIG. 2, there is shown is a schematic elevation view of one embodiment of the xerographic processing or printing section 3. The printing section 3 has a photoconductive belt 14 that advances in the direction of arrow 16. Photoconductive belt 14 passes through charging station 18 and exposure station 20 which is typically a raster output scanner that transmits a latent image from controller 22 onto the photoconductive surface of photoconductive belt 14. Controller 22 gets the image from raster input scanner 24 that typically incorporates a CCD and scans an image from document handler 26 Alternately, controller 22 gets the image from a separate computer 28 when printing section 3 operates as a printing device. Photoconductive belt 14 then advances to development station 30 where toner is electrostatically attracted to the latent image. Photoconductive belt 14 then advances to image transfer station 32. A sheet of material 34 is advanced from sheet stack 38 or sheet stack 40 by a sheet transport system 36 that includes registration system 42. Registration system 42 has a first drive 50 and a second drive 52 that is positioned downstream of first drive 50. Sheet 34 is advanced to registration system 42 that registers sheet 34 and then advances sheet 34 past image transfer station 32 in a timed fashion. The toner deposited on the latent image of photoconductive belt 14 is transferred to sheet 34 due to sheet 34 becoming charged at image transfer station 32 and due to sheet 34 being registered or timed relative to the latent image. Sheet 34 is then advanced to fusing station 44 by belt 46 where the toner image is permanently affixed to sheet 34, typically by heating, thus creating a document sheet. Sheet 34 will either be output to a finisher or a stacker or inverted at inverter 48 and recirculated through the printing section to have a second image deposited on its opposite side. Although the section 3 of the apparatus 2 has been described in detail above, features of the present invention could be used with other types of xerographic processing or printing sections having any suitably blank paper or sheet supply, created document output, image transfer system or paper path. The description above is merely intended to be exemplary. More or less features could also be provided. Although registration system 42 is shown at a fixed position within the copying or printing apparatus, this position is intended to be exemplary and various alternative locations and modifications can be devised by those skilled in the art without departing from the invention. Such an alternative, for example, would be incorporating registration system 42 at any point in the paper path of a copying or printing apparatus where the paper path is either upstream or downstream of the printing or copying operation. An additional alternative, for example, would be incorporating belts instead of rollers within registration system 42.

[0019] Referring now to FIG. 3, there is shown a schematic side view of the registration system 42 incorporating features of the present invention. Registration system 42 includes the first drive 50 and the second drive 52. First drive 50 has a first drive roll 62 and a first idler roll 64. Second drive 52 has a second drive roll 66 and a second idler roll 68. In each instance, the idler and drive rolls are urged against each other to allow sheets to be moved by frictional engagement between them. First drive roll 62 is driven by first motor 70. Controller 72 is connected to first motor 70. First motor 70 may be directly connected to first drive roll 62 or may be connected to additional drives or drive rolls in addition to first drive roll 62. Through first motor 70, controller can vary velocity 74 of first drive roller 62 either by varying the velocity of first motor 70, by mechanical speed reduction as with gearing, belt or a clutch, or otherwise. Second drive roll 66 is driven by second motor 76, a clutch 78 can be attached between second motor 76 and second drive roll 66. Clutch 78 can be connected to controller 72. Through clutch 78, controller 72 can intermittently drive second drive roll 66 between a stalled state where second drive roll 66 has zero velocity and a driving state where second drive roll 66 has a fixed velocity after it initially accelerates from the engagement of clutch 78. However, in an alternate embodiment, the clutch might not be provided. The registration system 42 further comprises a sheet sensor 82 baffles 86 and 88 which define a buckle chamber 89, and a buckle chamber sensor 91. As the sheet 80 enters the registration system 42, it is contacted by the two rolls 62, 64 of the first drive 50 and advanced by the first drive along the paper path toward the second drive 52 as indicated by arrow 90. Sheet of material 80 is driven by first drive 50 at a velocity that is proportional to velocity 74. Referring also to FIGS. 6 and 7, the velocities of the drive rolls 62, 66 and the lead edge 84 of the sheet 80 are shown on a time chart. The velocity of the drive roll 62 initially starts at zero and accelerates to a predetermined first velocity V1. Alternately, the velocity of the drive roll 62 initially may be running at a predetermined first velocity V1. The lead edge 84 of the sheet 80 enters the first drive 50 at time T1 and travels forward at velocity V1. Referring also to FIG. 4, at time T2 sensor 82 is triggered by the sheet 80. The sensor 82 could be any type of suitable sensor, such as an optical sensor for example. Sensor 82 detects when sheet of material 80 passes it and sends a signal to controller 72. Controller 72 is shown as a single controller, but may alternately be individual controllers, or logic circuits or part of an overall machine controller. Controller 72 reduces velocity 74 of first drive roller 62 when sensor 82 detects lead edge 84 as shown. Alternately, if sensor 82 is further upstream of the paper path, controller 72 will reduce velocity 74 of first drive roller 62 after a delay from the time when sensor 82 detects lead edge 84 or trailing edge 96. In this manner, sensor 82 may be placed upstream or downstream relative to drive roller 62. When velocity 74 of first drive roller 62 is reduced to about velocity V2, velocity of sheet 80 that is proportional to velocity 74 is also reduced. As a result, the velocity of the lead edge 84 of sheet of material 80 will be reduced to about V2 and the lead edge 84 of sheet of material 80 will not be damaged when it makes contact with non-moving or stalled second drive 52.

[0020] Referring also to FIG. 5, sheet of material 80 is driven by first drive 50 at velocity V2 past sensor 82 into second drive 52 while second drive 52 is in the stalled state. If sheet of material 80 was to contact non-moving or stalled second drive 52 at velocity V1, lead edge 84 could be damaged. To reduce the risk of damage to lead edge 84 at higher speed operation, the velocity of sheet of material 80 is reduced to levels (i.e.: velocity V2) just before lead edge 84 contacts the non-moving or stalled second drive 52 that do not produce damage to lead edge 84 as described herein. Lead edge 84 of sheet of material 80 comes up against the non-moving or stalled second drive 52 by time T3. Thus, at time T3 the velocity of the lead edge 84 has been reduced to zero. Because lead edge 84 is stopped and the drive 50 is continuing to move the sheet 80, the sheet buckles in the chamber 89. The sensor 91 can sense when a predetermined sheet buckling has occurred, such as disclosed in U.S. Pat. No. 5,775,690 which is hereby incorporated by reference in its entirety. However, any suitable delay system or system for activating the second drive 52 could be provided. After time T3, the velocity of the drive roll 62 can remain at V2 or start to increase back to Vi. At time T4, when the sensor 91 senses that the predetermined sheet buckling has occurred (or an otherwise delay from time T3), the controller 72 activates the motor 76 and clutch 78 such that the velocity of the drive roll 66 increases from zero towards V1. Through clutch 78, controller 72 can intermittently drive second drive roll 66 between a stalled state where second drive roll 66 has zero velocity and a driving state where second drive roll 66 has an increased velocity after it initially accelerates from the engagement of clutch 78.

[0021] Controller 72 is shown as a single controller, but may alternately be individual controllers, or logic circuits or part of an overall machine controller. After sheet of material 80 is deskewed with second drive 52 as described herein, and sheet 80 is registered or timed relative to the printing, copying or handling operation then sheet 80 is advanced with second drive 52. At time T5 the second drive roll 66 could reach velocity V1 and lead edge 84 would resume its movement at velocity V1. At time T6 (that may occur after time T3 but before, during or after time T4) the controller 72 could increase the velocity of drive roll 62 back to V1. Controller 72 intermittently drives second drive roll 66 from the stalled state where second drive roll 66 has zero velocity to a driving state where second drive roll 66 preferably has a fixed velocity 94 after it initially accelerates from the engagement of clutch 78. In this manner, sheet 80 is driven and handled within the printing, copying or handling operation in a registered and deskewed fashion by registration system 56. Sheet of material 80 is driven by first drive 50 past sensor 82 into second drive 52 while second drive 52 is in the stalled state. Sensor 82 detects when sheet of material 80 passes it and sends a signal to controller 72. Sheet of material 80 is deskewed as the body of sheet of material 80 pivots about in the buckle chamber formed by baffles 86 and 88. If sheet of material contacts non-moving or stalled second drive 52 at excessive speed, lead edge 84 could be damaged. To eliminate damage to lead edge 84, while still maintaining higher speed operation of the system, the velocity of sheet of material 80 is temporarily reduced to levels that do not produce damage to lead edge 84 just before lead edge 84 contacts the non-moving or stalled second drive 52. To reduce the velocity of sheet of material 80 to levels that do not produce damage to lead edge 84, controller 72 reduces velocity 74 of first drive roller 62 when sensor 82 detects lead edge 84. Alternately, if sensor 82 is further upstream of the paper path, controller 72 will reduce velocity 74 of first drive roller 62 after a delay from the time when sensor 82 detects lead edge 84 or trailing edge 96. In this manner, sensor 82 may be placed upstream or downstream relative to drive roller 62. After a period of time during which sheet of material 80 is deskewed and in contact with non moving or stalled second drive 52 as described herein, controller 72 increases velocity 74 of first drive roller 62. In this manner, lead edge 84 of sheet of material 80 will not be damaged yet the apparatus incorporating registration system 42 may be operated at higher speed overall as compared to existing stalled roll approaches. As a result, there is provided a sheet moving system which provides an increase in machine speed, but with the use of a low cost stalled roll registration apparatus such as described by registration system 42.

[0022] It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims. 

What is claimed is:
 1. A document creating apparatus comprising: an image transfer system for transferring an image onto a sheet of material; and a transport system for transporting the sheet of material along a paper path, the transport system comprising: a first drive located along the paper path for moving the sheet of material; a second drive located along the paper path downstream from the first drive for moving the sheet of material; and a controller connected to the first drive and adapted to vary a drive velocity of the first drive; wherein, while the sheet of material contacts the first drive, the controller decreases the drive velocity of the first drive before the sheet of material contacts the second drive, and wherein the controller increases the drive velocity after the sheet of material contacts the second drive.
 2. The document creating apparatus of claim 1 wherein the image transfer system comprises a printer.
 3. The document creating apparatus of claim 1 wherein the image transfer system comprises a xerographic toner depositor.
 4. The document creating apparatus of claim 1 wherein the first drive comprises a first idler roll and a first drive roll which transports the sheet of material along the paper path with a variable drive velocity.
 5. The document creating apparatus of claim 4 further comprising a motor connected to the first drive roll, wherein the motor is adapted to variably drive the first drive roll.
 6. The document creating apparatus of claim 1 wherein the second drive comprises a second drive roll and a second idler roll wherein the second drive roll is adapted to intermittent drive the sheet of material along the paper path.
 7. The document creating apparatus of claim 6 further comprising a motor and a clutch connected to the second drive roll, wherein the motor and the clutch are adapted to intermittently drive the second drive roll.
 8. The document creating apparatus of claim 1 further comprising a sensor adapted to sense a leading edge of the sheet of material before the sheet of material contacts the second drive.
 9. A stalled roll registration system for use in a document creating apparatus, the stalled roll registration system comprising: a first drive for driving a sheet of material within a paper path, the first drive comprising a first idler roll and a first drive roll which drives the sheet of material with a variable drive velocity; a second drive positioned downstream of the first drive within the paper path, the second drive comprising a second drive roll and a second idler roll with the second drive roll being adapted for intermittent driving; and a controller connected to the first drive and adapted to vary the drive velocity; wherein, while the sheet of material contacts the first drive, the drive velocity is decreased before the sheet of material contacts the second drive, and wherein the drive velocity is increased after the document sheet contacts the second drive.
 10. A document creating apparatus comprising the stalled roll registration system of claim 9 and a printer.
 11. A document creating apparatus comprising the stalled roll registration system of claim 9 and a xerographic toner depositor.
 12. The stalled roll registration system of claim 9 wherein the first drive further comprises a motor connected to the first drive roll, wherein the motor is adapted to drive the first drive roll with a variable velocity.
 13. The stalled roll registration system of claim 9 wherein the second drive further comprises a motor and a clutch connected to the second drive roll, wherein the motor and the clutch are adapted to intermittently drive the second drive roll.
 14. The stalled roll registration system of claim 9 further comprising a sensor adapted to sense a leading edge of the sheet of material before the sheet of material contacts the second drive.
 15. A method of moving a sheet of material in a document creating apparatus comprising the steps of: driving a first drive at a first drive velocity to move a sheet of material at a first speed; when a leading edge of the sheet of material approaches a second drive, decreasing velocity of the first drive to a slower second drive velocity to thereby move the sheet of material at a slower second speed before the sheet of material contacts the second drive; and after the sheet of material contacts the second drive, increasing velocity of the first drive to a third drive velocity which is faster than the slower second drive velocity.
 16. The method of claim 15 further comprising the step of sensing the leading edge of the sheet of material before the sheet of material contacts the second drive and while the sheet of material contacts the first drive.
 17. A method of copying an image comprising the method of claim 15 and the step of xerographic copying an image onto the sheet of material before or after the sheet of material contacts the first drive.
 18. A method of printing an image comprising the method of claim 15 and the step of printing on the sheet of material before or after the sheet of material contacts the first drive.
 19. The method of claim 15 further comprising the step of driving the second drive to move the sheet of material after the step of increasing velocity of the first drive to the third drive velocity which is faster than the slower second drive velocity. 